Embodiments generally relate to a system and method of controlling a fan array, and, more particularly, to a system and method of minimizing vibrations within a fan array.
Enclosed structures, such as occupied buildings and factories, for example, generally include a heating, ventilating, and air conditioning (HVAC) system for conditioning ventilated and/or recirculated air in the structure. A typical HVAC system includes a supply air flow path and a return and/or exhaust air flow path. The supply air flow path receives air, for example outside or ambient air, re-circulated air, or outside or ambient air mixed with re-circulated air, and channels and distributes the air into the enclosed structure. The air is conditioned by the HVAC system to provide a desired temperature and humidity of supply air discharged into the enclosed structure. The exhaust air flow path discharges air back to the environment outside the structure, or ambient air conditions outside the structure.
Air-handling systems (also referred to as “air handlers”) have traditionally been used to condition buildings or rooms (hereinafter referred to as “structures”). An air-handling system includes components designed to operate together in order to condition air as part of a primary system for ventilation of structures. The air-handling system may include cooling coils, heating coils, filters, humidifiers, fans, sound attenuators, controls, and other devices functioning to meet the needs of the structures.
Some air-handling systems include an array of fan units. Each fan unit includes a fan operatively connected to a motor, which drives the fan. During operation, each fan unit produces a certain amount of residual vibration. Residual vibration is the amount of vibration present in an operating system after standard balancing procedures are completed, and the fan unit is certified for use.
Vibration energy from fan units within an array, mounted to a common structure, such as a frame, is additive at certain points of operation. The additive effect of fan vibration increases when one or more fans are in-phase with one another. Generally, each fan has a certain amount of residual imbalance due to a mass located at a position that is not at the center of rotation. If the mass center of rotation is not coincident with the physical center of rotation, the assembly will not be balanced. When fans are commonly oriented such that their mass centers are at the same radial positions relative to one another, the fans are in-phase. In general, when the mass centers of fans of a fan array are in-phase with one another, the fan array generates a maximum vibration, which may then be transmitted to the support structure of the air-handling system, and ultimately to a structure, such as a floor or roof, that supports the air-handling system. The additive vibrational energy may produce undesirable vibration in a building. Conversely, when the mass centers are 180 degrees out-of-phase relative to one another, the amount of force due to operation of the fans is minimal.